IDEAL House – New Zealand

Project Goals: Certified Passive House, Positive Energy & 8/10 Homestar design. Proudly supported by IDEAL Electrical Suppliers.

Slab Engineering


Thanks to the assistance of Wilton Joubert, we have now completed the last piece of design/engineering – the concrete slab. The architects, Matt and Stephen from S3 are now adding the slab details to the working drawings and we plan to be ready to lodge consent by the end of the week.

We are using a polystyrene pod system, based on the original Rib Raft which was designed by Firth, and incorporating reinforcing bar (EuroSteel) and mesh (Xtra Ductile G500E) from EuroCorp.

The slab has been designed to handle the weight of the solar panels on the roof (40 panels at about 21kg each), in a high wind zone, and load bearing walls that have come about to support the mezzanine floor and wider spans inside.


As the garage is outside the thermal envelope, we have also had to add in a step down to incorporate the extra thickness of the batten and cradle system we’re using to insulate the main slab (above the concrete).


The drawings also show our nib which will run around the outside of the slab edge, again allowing for the batten and cradle system to sit on the inside of this nib.

ImageFull slab documents can be viewed here:

Plans and details


Drainage details

Producer Statement

2 thoughts on “Slab Engineering

  1. Curious, as to whether you’ve insulated the perimeter of your concrete slab?

    • Rather than trying to insulate underneath, and around the outside, we have decided to insulate above the slab. This is common in Europe where they break the slab with some form of polystyrene or polyurethane (PU) layer, and then screed over the top. Instead we’re using more traditional insulation (Earthwool) on the main area, and then a 40/50mm PU strip around the inside of the nib. We’ll have some detailed photos as we do this.

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